The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
Solid oxide fuel cells can generate electricity by electrochemically reacting an oxidant and fuel. Solid oxide fuel cells can be adapted to operate utilizing various fuel compositions including fuels that are commercially available. Exemplary fuels include various hydrogen-containing molecules and mixtures of hydrogen-containing molecules.
Hydrocarbon-based fuels such as fuels that contain propane, butane, and blends of propane and butane, with or without other components are commercially available worldwide. Solid oxide fuels cells can utilize these hydrocarbon-based fuels to generate electricity. Using fuel that is locally commercially available can be advantageous over using fuel that is specifically formulated for fuel cells in that separate distribution networks do not need to be established when utilizing fuels that are already commercially available in the marketplace.
The composition of commercially available fuel can differ in fuel grade, composition of hydrocarbons, fuel purity level, poison level, contamination level, particulate level, and level of fuel additives. In particular, fuel compositions can differ between grades or classifications of fuels or can different within a grade or a classification, that is, a grade or classification specification can allow for ranges of fuel component levels.
For example, in the United States there are multiple grades of commercial propane containing varying amounts of propane, butane, and other light hydrocarbons. Further, fuel compositions can differ based on different fuel composition standards in different parts of the world. For example, the composition of liquefied petroleum gas (‘LPG’), an exemplary solid oxide fuel cell fuel that typically includes propane and/or butane, can vary by a broad range based on regional or country-specific standards.
Fuel can be refined prior to utilization for electrochemical reactions within a solid oxide fuel cell. An internal fuel refining member (for example, a fuel filter) can convert a raw fuel introduced to the fuel cell system to a refined fuel. The refined fuel can provide increased fuel cell performance and fuel cell operating life when compared with the unrefined fuel. The fuel filter and refinement method can be optimized based on the raw fuel composition, impurities levels, and fuel additives. Further, system controls can be optimized based on the raw fuel composition and based on the fuel cell system's capability in refining the raw fuel to the refined fuel.
Fuel can be routed through a fuel filter prior to being routed to the fuel cell to remove potential poisons, contaminants, non-fuel molecules, debris, or other undesirable components contained within the raw fuel. However, if the fuel filter does not have sufficient poison removal properties to refine the fuel, poisons, debris, contaminants, or additives can pass through the fuel filter and degrade the operational performance of the fuel cells.
Since commercially available fuels vary widely in composition, filter design and filtering media composition can vary widely for optimization with the specific fuel composition. For example, a fuel filter may not efficiently remove poisons if the fuel filter is incompatible with the specific fuel utilized or if the fuel filter is utilized beyond the fuel filter's operational lifetime. Further, the wide range of fuel compositions can lead to an undesirably high probability that a fuel filter that is not sufficiently compatible with the fuel composition will be utilized within the fuel cell system, due to, for example, misidentification of fuel or user error. Still further, in order to accommodate a wide-range of fuel compositions, fuel filters can be over-engineered with filtering or poison removal materials that are not utilized for the specific fuel composition, thereby increasing the cost of the fuel filter.
Therefore, improved fuel cell systems utilizing commercially available fuels and improved methods for operating fuel cells with commercially available fuels are needed.
It should be understood that the appended drawings are not necessarily to scale, presenting a somewhat simplified representation of various preferred features illustrative of the basic principles of the invention. The specific design features of the fuel cell will be determined in part by the particular intended application and use environment. Certain features of the illustrated embodiments have been enlarged or distorted relative to others for visualization and understanding. In particular, thin features may be thickened for clarity of illustration. All references to direction and position, unless otherwise indicated, refer to the orientation of the solid state electrochemical device illustrated in the drawings.